John Ensign (born March 25, 1958) is the junior United States Senator from Nevada. He is a member of the Republican Party. He was born in Roseville, California, but he and his family moved to Nevada when he was a child. He went to universities in Nevada, Oregon, and Colorado, becoming a veterinarian in 1985. He then became a successful businessman, opening a 24-hour animal hospital in Las Vegas. Senator Ensign spends his workweek in Washington and his weekends in Las Vegas with his wife, Darlene, and their three children - Trevor, Siena, and Michael. He is a devout Christian and attends a Foursquare church in northwest Las Vegas.

He quickly became successful at politics, being elected to the United States House of Representatives in the Republican landslide 1994 Congressional election. He was reelected in 1996 but declined to run again in 1998. Instead he ran for the Senate but was defeated by the Democratic incumbent, Harry Reid. He gained a Senate seat after his second try in 2000, defeating Democratic opponent Ed Bernstein, to succeed the retiring Democratic incumbent, Richard H. Bryan.

Ensign has become a leading voice against the Kelo v. New London Supreme Court ruling, and has announced plans to introduce a bill that would strongly blunt the effects of the ruling.

Senator Ensign has been praised by many organizations for his support for fiscal conservatism. In 2003, the American Conservative Union named Ensign along with Senators Chuck Hagel (NE) and Don Nickles (OK) as the most conservative Senator in 2003. Ensign failed to achieve the award in 2004, receiving a 92core. His accolades for 2004 include being named, along with Senator Jon Kyl (AZ), the most taxpayer-friendly senator by the National Taxpayers Union. Ensign also received the highest rating for a senator by the Citizens Against Government Waste, while being hailed as a "Taxpayer's Hero" for his lifetime efforts against government waste. Both Citizens for a Sound Economy, whose chairman is former House Majority Leader Dick Armey, and the National Tax Limitation Committee gave Senator Ensign their highest ratings.

On the morning of January 30, 2006, Senator Ensign and an aide were involved in a traffic accident in Las Vegas after their car was struck by an oncoming car on their way to the airport. Both suffered minor injuries.

For a short time in March 2006, Senator Ensign blocked the nomination of VADM Thad Allen to become the next Commandant of the United States Coast Guard. . VADM Allen was the principal federal official following the Katrina hurricane, replacing FEMA director Brown.